cmd/guru: fix typo of 'hyphen' to rename to 'comma'
cmd/guru: fix typo of 'hyphen' to rename to 'comma'

start|end byte offset separator is not hyphen(-), actually comma(,)

Change-Id: I344ae74d33863e9456e8cdb2f058fd70f1eedf95
Reviewed-on: https://go-review.googlesource.com/35770
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/tools,golang/tools,golang/tools,syreclabs/go-tools,golang/tools,syreclabs/go-tools,golang/tools,syreclabs/go-tools,syreclabs/go-tools,syreclabs/go-tools,syreclabs/go-tools